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1、例11-1 一根装有两个斜齿轮的轴由一对代号为7210AC的滚动轴承支承。已知两轮上的轴向力分别为F a1 = 3000 N,F a2 = 5000 N,方向如图。轴承所受径向力R 1= 8000 N,R 2 = 12000 N。冲击载荷系数 fd = 1,其它参数见附表。求两轴承的当量动载荷P 1、P 2。例11-1图1 解:1求内部派生轴向力S 1、S 2的大小方向S1 = 0.68R1 = 0.688000 = 5440 NS2 = 0.68R2 = 0.6812000 = 8160 N,方向如图所示。2求外部轴向合力F AFA= Fa2F a1 = 50003000 = 2000 N,
2、方向与F a2的方向相同,如图所示。3求轴承所受的轴向力A 1、A 2 S 2 + FA = 8160 + 2000 = 10160 N,S 2 + FAS 1 = 5440 N,轴承1被压紧。 A 1= S2 + FA = 10160 N,A 2 = S2 = 8160 N4轴承的当量动载荷P 1、P 2据:A 1/ R1 = 10160/8000 = 1.27e = 0.68,得:X 1 = 0.41,Y 1 = 0.87P1 = fd(X 1 R1 + Y1 A1)= 0.418000 + 0.8710160 = 12119 N据:A 2/ R2 = 8160/12000 = 0.68
3、= e,得:X 2 = 1,Y 2 = 0P2 = fd(X 2 R2 + Y2 A2)= 8000 N例11-3 某轴由一对代号为30212的圆锥滚子轴承支承,其基本额定动载荷C = 97.8 kN。轴承受径向力R 1= 6000N,R 2 =16500N。轴的转速 n =500 r/min,轴上有轴向力F A = 3000 N,方向如图。轴承的其它参数见附表。冲击载荷系数 fd = 1。求轴承的基本额定寿命。例11-3 图1解:1求内部派生轴向力S 1、S 2的大小方向N05.621YRNS A/Re A/Re eX Y X Y0.68R1 0 0.41 0.870.68例 11-1 图
4、2S A/Re A/Re eX Y X YR21 0 0.4 1.50.40例 11-3 图 2方向如图所示。2求轴承所受的轴向力A 1、 A2公式归纳法: N ,maxFS2503502max ,N, 2 3轴承的当量动载荷P 1、P 2据:A 1/ R1 = 2500/6000 = 0.417e = 0.40,得:X 1 = 0.4,Y 1 =1.5P1 = fd(X 1 R1 + Y1 A1)= 0.46000 + 1.52500 = 6150 N据:A 2/ R2 = 5500/16500 = 0.33 e,得:X 2 = 1,Y 2 = 0P2 = fd(X 2 R2 + Y2 A2
5、)= R 2 = 16500 N P2P 1,用 P2 计算轴承寿命。4计算轴承寿命12562 h3106610 59780CnLh例11-4 一传动装置的锥齿轮轴用一对代号为30212的圆锥滚子轴承支承,布置如图。已知轴的转速为1200r/min,两轴承所受的径向载荷R 1= 8500N, R2 =3400N。f d = 1,常温下工作。轴承的预期寿命为15000小时。试求:1允许作用在轴上的最大轴向力 F A2滚动轴承所受的轴向载荷 A 1、A 2解:由轴承手册查得30212C轴承: C = 97800 N,e = 0.4,X = 0.4,Y = 1.5N2835.1021YRSN4 S
6、1S 2, S 1+ FAS 2,轴承2被压紧。A1 = S1 = 2833 N ,A 2= S1 + FA, e = 0.42222 83.0348RFRRAA X 2 = 0.4,Y 1 = 1.5即: P2 = fd(X 2 R2 + Y2 A2)= 0.43400 + 1.5A 2根据: 1500,CnLh601P 12031 N3103/10652978h由: P2 = 0.43400 + 1.5A2 12031解得: A2 7114 N再据: A2 = S1 + FA解得: FA= A2S 1 = 71142833 = 4281 N例 11-4 图 1例 11-4 图 2验算轴承1
7、的寿命:A1/R1 = S1/R1 = 2833/8500 = 0.33 0.4,X 1 = 1,Y 1 = 0P1 = fd(X 1 R1 + Y1 A1)= R 1 = 8500 N因: P1 P2,轴承1的寿命大于15000小时。例11-5 某轴的轴承组合如图例11-4 图1,两轴承的代号为6313,布置如图。已知轴的转速为485r/min,轴承所受的径向力分别为R 1= 5500N,R 2 =6400N。轴上有轴向力F A = 2200N,方向如图。常温下工作,有轻微冲击。试求轴承的寿命。解:图示轴系结构为单支点双向固定(固游式)结构。轴承1为固定端,轴承2为游动端。轴上的轴向载荷F
8、A由固定端轴承轴承1来承受,游动端轴承不承受轴向力。即:A 1 = FA = 2200 N ,A 2 = 0由轴承手册查得6313轴承:C = 72200 N,C 0 = 56500 N。对轴承1:A 1 = 2200 N,R 1= 5500NA1/C0 = 2200/56500 = 0.039,查得:e 1 = 0.24A1/R1 = 2200/5500 = 0.4 e1 = 0.24,查得:X 1 = 0.56,Y 1 =1.85因载荷有轻微冲击,查取冲击载荷系数:f d = 1.2P1 = fd(X 1 R1 + Y1 A1)=1.2(0.565500 + 1.852200)= 8580 N对轴承2:A 2 = 0,R 2 =6400N,X 2 = 1,Y 2 =0P2 = fd(X 2 R2+ Y2 A2)= 1.2 R 2 =1.26400 = 7680 N因:P 1P 2,用P 1计算轴承寿命:= = 20476 hCnLh603685074 例 11-5 图